1. Technical Field
The present disclosure relates to an electromagnetic input device and a coil detection circuit thereof, in particular, to an electromagnetic input device having a plurality of loop coils, and a coil detection circuit thereof.
2. Description of Related Art
People can interact with electronic devices via an input device, such as a touch panel, wherein the touch panels with advances in technology, have been widely used in electronic devices, such as smart phones, tablet computers, auto teller machines (ATMs) or computer graphics tablets, etc. Thus, people can easily touch the touch panel to generate an input signal to an electronic device so as to enhance the ease of operation of the electronic device
However, to enhance the touch sensing ability of the touch panel, the induction lines in touch panel are closely distributed in a certain area of the transparent conductive film, such as an indium tin oxide (ITO) film, or in a certain area of the metal pattern layer of a substrate. Because the induction lines are in a interlaced and tight distribution, an induction line shorting or opening condition may occur in the sensing circuit of the input device, and the ease of usage of the touch panel is thus reduced.
Moreover, a conventional detection device or coil detection circuit includes, for example, a voltage source and a plurality of indicator lights, so as to test the input device (such as the touch panel), wherein the voltage source is connected to one terminal of each induction line, and each of the indicator lights is correspondingly connected between another terminal of the corresponding induction line and a common ground terminal. If an induction line opening condition occurs, the indicator light connected to the corresponding induction line will not light up so that the operator can determine the corresponding induction line is in an open circuit state.
Although the conventional detection device can detect the induction line opening condition, the detection device neither can identify whether there is an induction line shorting condition occurs in the adjacent or interleaved induction lines nor identify whether the impedance of each of the induction lines falls within a specified range. If an induction line shorting condition occurs in one induction line and another induction line which is adjacent to or vertically staggered with respect to the induction line, the conventional detection device cannot detect the induction line shorting condition. For example, when one X-axis direction induction line connects with another X-axis direction induction line which is adjacent to the X-axis direction induction line (i.e. the induction line shorting condition occurs), the indicator light still lights up, but the induction line shorting condition should not exist in the touch panel.
In addition to the induction line shorting condition cannot be detected, whether the impedance of each of the induction lines is abnormally high or low cannot be identified either even the induction lines are determined to be normal under the induction line opening condition test. However, the impedance abnormality in the corresponding induction line will still affect the operation of the input device (such as the touch panel).